Among fluorine-containing organic compounds (fluorocarbons), organic compounds having a double bond in a molecule are known to have a very short atmospheric lifetime because of the double bond and have substantially no influence on global warming and depletion of ozone layer, and thus to be useful as a functional substance such as a washing detergent, a solvent, a foaming agent, a coolant, a spray, a working fluid or the like or as an intermediate for any of various functional products.
Organic compounds which are known to contain fluorine having a double bond in a molecule include, for example, 1-chloro-3,3,3-trifluoro-1-propene and 1,3,3,3-tetrafluoropropene. The following methods for producing 1,3,3,3-tetrafluoropropene are disclosed. Izvest. Akad. Nauk S.S.S.R., Otdel. Khim. Nauk. page 1312, 1960 discloses a method by which 1,1,1,3,3-pentafluoropropane is subjected to dehydrofluorination by use of potassium hydroxide in dibutylether. Japanese Patent Laid-Open No. H10-7605 discloses a method by which 1-chloro-3,3,3-trifluoropropene is fluorinated by hydrogen fluoride in the presence of a Ti/C catalyst or a Cr/C catalyst. Japanese Patent Laid-Open No. H11-140002 discloses a method by which 1,1,1,3,3-pentafluoropropane is put into contact with carbon or metal-supported carbon in a reaction temperature range raised by a gas phase to cause dehydrofluorination.
Japanese Patent Laid-Open No. H9-183740 discloses a method by which 1,1,1,3,3-pentachloropropane is reacted with hydrogen fluoride in a gas phase to produce 1-chloro-3,3,3-trifluoro-1-propene. Japanese Patent Laid-Open No. H11-180908 discloses a method by which 1,1,1,3,3-pentachloropropane is reacted with hydrogen fluoride with no catalyst to produce 1-chloro-3,3,3-trifluoro-1-propene.
An organic compound containing fluorine and having a double bond in a molecule such as 1-chloro-3,3,3-trifluoro-1-propene, 1,3,3,3-tetrafluoropropene or the like contains cis-trans isomers. By the methods for producing 1,3,3,3-tetrafluoropropene disclosed in Japanese Patent Laid-Open No. H10-7605, Japanese Patent Laid-Open No. H11-140002 and Izvest. Akad. Nauk S.S.S.R., Otdel. Khim. Nauk. page 1312, 1960 described above, 1,3,3,3-tetrafluoropropene is usually obtained in the form of a mixture of a cis isomer (hereinafter, may be referred to as “1234Z”) and a trans isomer (hereinafter, may be referred to as “1234E”) (hereinafter, the mixture of 1234E and 1234Z may be referred to as “1234” or “1234EZ”; or in the case where it is not intended to distinguish whether the isomer is a cis isomer or a trans isomer, the isomer will be referred to as “1234” or “1234EZ”). Similarly, by the methods for producing 1-chloro-3,3,3-trifluoro-1-propene disclosed in Japanese Patent Laid-Open No. H9-183740 and Japanese Patent Laid-Open No. H11-180908, 1-chloro-3,3,3-trifluoro-1-propene is usually obtained in the form of a mixture of a cis isomer (hereinafter, may be referred to as “1233Z”) and a trans isomer (hereinafter, may be referred to as “1233E”) (a mixture of 1233Z and 1233E may be referred to as “1233” or “1233EZ”; or in the case where it is not intended to distinguish whether the isomer is a cis isomer or a trans isomer, the isomer will be referred to as “1233” or “1233EZ”). The trans isomer, which is thermodynamically stable, is a main component in obtained 1-chloro-3,3,3-trifluoro-1-propene. However, in an organic compound containing fluorine and having a double bond in a molecule, either one of the cis isomer or the trans isomer may be used.
In the case of, for example, 1-chloro-3,3,3-trifluoro-1-propene, the trans isomer and the cis isomer have different boiling points (the boiling point of the trans isomer is 19° C.; and the boiling point of the cis isomer is 39° C.). Whether the trans isomer is desired or the cis isomer is desired depends on the use of 1-chloro-3,3,3-trifluoro-1-propene. When 1-chloro-3,3,3-trifluoro-1-propene is used for a washing detergent or the like, the cis isomer (boiling point: 39° C.), which is easy to handle at room temperature, is mainly used from the viewpoint of volatility. By contrast, when 1-chloro-3,3,3-trifluoro-1-propene is used for a foaming agent or the like, the trans isomer (boiling point: 19° C.) is mainly used. Japanese Patent Laid-Open No. 2008-285471 discloses a method for producing 3,3,3-trifluoropropyne, by which cis-1-halogeno-3,3,3-trifluoropropene is reacted with a base. It is described that when the trans isomer is used as a material, the reaction does not progress at all; whereas when the cis isomer is used as a material, trifluoropropyne is obtained at a high yield. As can be seen from this, the cis isomer and the trans isomer have different properties.
As can be seen, the compound obtained by the production method disclosed in each of Japanese Patent Laid-Open No. H10-7605 through Japanese Patent Laid-Open No. H11-180908 and Izvest. Akad. Nauk S.S.S.R., Otdel. Khim. Nauk. page 1312, 1960 has a double bond in a molecule and thus is a mixture of a cis isomer and a trans isomer. This is disadvantageous in the case where either one of the cis isomer or the trans isomer is desired.
In such a situation, it has been attempted to perform mutual conversion of a cis isomer and a trans isomer of an organic compound containing fluorine and having a double bond in a molecule by use of an isomerization reaction. For example, Japanese Patent Laid-Open No. 2010-523635 discloses a method by which E-(hydrohalo)fluoroalkene, which is a trans isomer, is put into contact with a solid catalyst such as a Lewis acid catalyst, a chromia-containing catalyst, an alumina catalyst or the like by a gas phase reaction by utilization of an equilibrium reaction to be isomerized into Z-(hydrohalo)fluoroalkene, which is a cis isomer. Japanese Patent Laid-Open No. 2009-108049 discloses a method by which cis-1,3,3,3-tetrafluoropropene is put into contact with a solid catalyst such as a fluorinated chromia catalyst, an aluminum fluoride catalyst or the like by a gas phase reaction by utilization of an equilibrium reaction to be isomerized into trans-1,3,3,3-tetrafluoropropene. Japanese Patent Laid-Open No. 2012-509324 discloses a method by which cis-1-chloro-3,3,3-trifluoropropene is isomerized into trans-1-chloro-3,3,3-trifluoropropene in the presence of a homogenous or non-homogenous catalyst. It is also disclosed that an oxidizer such as oxygen or chlorine is added in order to extend the life of the catalyst. Japanese Patent Laid-Open No. 2012-512160 discloses a mutual conversion method by which trans-1-chloro-3,3,3-trifluoropropene or cis-1-chloro-3,3,3-trifluoropropene is isomerized on a surface of a heated solid catalyst or the like in a specific temperature range by utilization of an equilibrium reaction. United States Patent Application Publication No. 2010/0152504 discloses an isomerization method by which trans-1-chloro-3,3,3-trifluoropropene is converted into cis-1-chloro-3,3,3-trifluoropropene by utilization of an equilibrium reaction. Journal of the American Chemical Society, vol. 15, pp. 3314-3319 (1965) discloses an example in which the isomerization rate of 1,3-pentadiene is examined by use of nitrogen monoxide (NO) as a radical source. However, as shown by the Markovnikov's rule or the anti-Markovnikov's rule, olefin formed of only hydrocarbon such as 1,3-pentadiene or the like and olefin containing a plurality of halogen atoms as substituents often exhibit different reaction behaviors. No case has been reported in which an olefin containing a plurality of halogen atoms as substituents such as 1-chloro-3,3,3-trifluoropropene or the like is isomerized by a radical. Japanese Patent Laid-Open No. 2010-202640 discloses a method for purifying cis-1-chloro-3,3,3-trifluoropropene.
Japanese Patent Laid-Open No. 2010-523635 discloses a method by which trans-(hydrohalo)fluoroalkene is put into contact with a solid catalyst such as a Lewis acid catalyst, a chromia-containing catalyst, an alumina catalyst or the like to be isomerized into cis-(hydrohalo)fluoroalkene by a gas phase reaction. However, a fluoroalkene such as 1,3,3,3-tetrafluoropropene or the like has a double bond between carbon atoms, and therefore is likely to be coked on a surface of a solid catalyst such as an alumina catalyst or the like. Since such a fluoroalkene covers an active point to reduce catalyst activity over time, the catalyst is inevitably deteriorated. This has a problem that the catalyst needs to be regenerated.
Japanese Patent Laid-Open No. 2009-108049 discloses a method by which cis-1,3,3,3-tetrafluoropropene is put into contact with a solid catalyst such as a fluorinated chromia catalyst, an aluminum fluoride catalyst or the like by a gas phase reaction to be isomerized into trans-1,3,3,3-tetrafluoropropene. As described above, a fluoroalkene such as 1,3,3,3-tetrafluoropropene or the like has a double bond between carbon atoms, and therefore is likely to be coked on a surface of a solid catalyst such as an alumina catalyst or the like. Since such a fluoroalkene covers an active point to reduce catalyst activity over time, the catalyst is inevitably deteriorated. This has a problem that the catalyst needs to be regenerated.
A Boltzmann distribution of 1,3,3,3-tetrafluoropropene was found by a hybrid functional method (B3LYP/6−311+G**) (see FIG. 1). According to the Boltzmann distribution, on the low temperature side, the abundance ratio of the trans isomer) (1234E), which was thermodynamically stable, was predominant. It is possible to perform an isomerization reaction of a trans isomer (1234E) into a cis isomer (1234Z) or of a cis isomer (1234Z) into a trans isomer (1234E) with no use of a solid isomerization catalyst. However, such a catalyst-free isomerization reaction has a problem of not being efficient because the conversion ratio of the trans isomer is several percent as the one-pass yield (yield per cycle) and thus the same reaction needs to be repeated several times to several ten times in order to obtain a practically high yield of the cis isomer (composition close to equilibrium). Similarly, in the case of such a catalyst-free isomerization reaction, the conversion ratio of the cis isomer (1234Z) is several percent as the one-pass yield and thus the same reaction needs to be repeated several times to several ten times in order to obtain a practically high yield of the trans isomer (composition close to equilibrium).
Japanese Patent Laid-Open No. 2012-509324 discloses a method by which cis-1-chloro-3,3,3-trifluoro-1-propene is isomerized into trans-1-chloro-3,3,3-trifluoro-1-propene in the presence of a solid catalyst such as an alumina catalyst or the like. However, as described above, a fluoroolefin having a double bond is, in general, likely to be coked on a surface of a solid catalyst. Since such a fluoroolefin covers an active point to reduce catalyst activity over time, the catalyst is inevitably deteriorated. Thus, the catalyst needs to be regenerated.
Japanese Patent Laid-Open No. 2012-512160 discloses a mutual conversion method of isomers of 1-chloro-3,3,3-trifluoro-1-propene. Example 2 describes an example of isomerizing a trans isomer into a cis isomer in the absence of a catalyst. A Boltzmann distribution of 1-chloro-3,3,3-trifluoro-1-propene was found by a hybrid functional method (B3LYP/6−311+G**) (see FIG. 1). According to the Boltzmann distribution, on the low temperature side, the abundance ratio of the trans isomer)(1234E), which was thermodynamically stable, was predominant. It is possible to perform an isomerization reaction of a trans isomer (1233E) into a cis isomer (1233Z) or of a cis isomer (1233Z) into a trans isomer (1233E) with no use of a solid isomerization catalyst. However, such a catalyst-free isomerization reaction has a problem of not being an efficient process because the conversion ratio of the trans isomer is merely 1 to 2% as the one-pass yield and thus the same reaction needs to be repeated several times to several ten times in order to obtain a practically high yield of the cis isomer (composition close to equilibrium). Similarly, in the case of such a catalyst-free isomerization reaction, the conversion ratio of the cis isomer is several percent as the one-pass yield and thus the same reaction needs to be repeated several times to several ten times in order to obtain a practically high yield of the trans isomer (composition close to equilibrium).
In a comparative example in Japanese Patent Laid-Open No. 2012-512160, trans-1-chloro-3,3,3-trifluoro-1-propene having bromine added thereto is irradiated with light in a liquid phase in an attempt to realize isomerization into a cis isomer. However, the conversion ratio is low and it is difficult to obtain a practically high yield.
In United States Patent Application Publication No. 2010/0152504, 1-chloro-3,3,3-trifluoro-1-propene is put into contact to a surface of a catalyst or the like that is heated to a temperature in a limited range of 150° C. to 350° C. to perform an isomerization reaction. In the presence of a catalyst, the isomerization progresses quickly up to a point of thermodynamic equilibrium or in the vicinity thereof. By contrast, a catalyst-free isomerization reaction is not efficient because the conversion ratio of the trans isomer is about 2% per pass and thus the same reaction needs to be repeated several times to several ten times in order to obtain a practically high yield. In addition, United States Patent Application Publication No. 2010/0152504 does not include any description on a method for highly purifying the cis isomer, which is the target compound.
In such a situation, an efficient mutual conversion method of cis-trans isomers of an organic compound containing fluorine and having a double bond in a molecule such as 1-chloro-3,3,3-trifluoro-1-propene, 1,3,3,3-tetrafluoropropene or the like regardless of presence/absence of a solid catalyst is now desired.